The part covering the period from A. D. 1259 to A. D. 1307 is largely a contemporaneous record
Matthew of Westminster, "an imaginary name given to a supposed author of a chronicle called 'Flores historiarum'; it is affixed to a manuscript of the 'Flores', probably written early in the fifteenth century ..
The 'Flores' was partly compiled and partly composed by varous writers at St. Alans and Westminster",--Dict. nat. biog
For a history of the work, cf. Dict. nat. biog. and the authorities to which it refers